两例Silver-Russell综合征的临床特征和H19印迹基因甲基化分析

目的探讨Silver-Russell综合征的遗传学异常，提高对该病的认识并指导临床诊断。方法以2例疑似Silver-Russell综合征患者为研究对象，详细采集病史并进行归纳，同时取其外周血用基因组DNA试剂盒提取DNA并用亚硫酸氢盐转化处理，然后用PCR扩增目标序列，采用焦磷酸测序法检测11P15区的H19印迹基因上游的DMR区的甲基化状态。另收集10例健康儿童外周血标本作为对照组。结果2例患儿的临床特征及辅助检查均符合Silver-Russell综合征临床诊断，所测的H19印迹基因上游的DMR区6个甲基化位点的甲基化水平分别为16％～21％和15％-23％，该区域均表现出低甲基化状态；而正常对照组的6个甲基化位点的甲基化水平为48％～55％，明显高于病例组。结论Silver-Russell综合征临床表现多样，运用焦磷酸测序技术联合甲基化分析操作方便、定量准确，可考虑对临床诊断或疑似Silver-Russell综合征病例运用该技术进行检测。

Clinical manifestations and analysis of methylation of H19 imprinted genes of two cases of Silver-Russell syndrome

Objective To investigate the genetic abnormalities of Silver-Russell syndrome, to improve the understanding of this disease, and to guide the clinical diagnosis. Methods Two patients who were suspected to have the Silver-Russell syndrome were selected and their medical history was collected in detail and summarized. The DNA of peripheral blood of patients was extracted by the genomic DNA kit and then prepared by the bisulphite conversion process. The target sequence was amplified by the PCR. The methylation status of DMR zone in upstream of H19 imprinted genes of 11P15 area was detected by the pyrophosphate sequencing. The peripheral blood of ten healthy children was collected as controls. Results The clinical characteristics and assistant examinations of two patients accorded with the clinical diagnosis of Silver-Russell syndrome. The methylation levels of six methylation sites of DMR zone in upstream of H19 imprinted genes were 16% -21% and 15%-22%. The methylation status of these areas was low. While the methylation levels of six methylation sites of controls were 48% -55%, which were significantly higher than those of patients. Conclusion The clinical manifestations of Silver-Russell syndrome are diverse. The pyrophosphate sequencing combined with the methylation analysis is easy to operate and can quantify accurately. This technology can be used for examining cases that are clinically diagnosed as Silver-Russell syndrome or suspected to have the Silver-RusseU syndrome.